Radiation pattern

[wavrider]

Dipole Antenna Radiation Patterns by WB4YJT

Open round table discussion here.

Looking for input and opinions.

Reading the link above it looks like the best height for a radiation pattern of a dipole is 1/2 WL above ground.

Would this also hold true for a yagi?

http://www.arrl.org/files/file/QEX_Next_Issue/May-Jun_2011/QEX_5_11_Siwiak.pdf

This link states that 1.5 to 1.6wl is best height above ground for DX.

The previous link shows 1.5 wl above ground not so good a pattern.

I use a MosleyPRO67B at 55' above earth ground. Works great 10 though 17 meters and pretty decent on 20 meters. Just a cloud warmer on 40 meters per say.

I am thinking of raising it another 20' to 30' in height. Not an issue I use a hazer to raise and lower the yagi and the tower is on a tilt plate.

Will the performance on the higher bands start to suffer due to height above ground? I have always understood that higher is better, within reason.

Or leave the yagi at 55' install another tower to 90' and use dipoles?

Then again the first link says above 1/2 wl the pattern gets skewed?

Opinions or thoughts?

 

[Robb]

Nothing says great DX better than a low angle of radiation from the antenna at 3/4 of a wave length high/higer for what ever band you have in mind - IMO . . .

 

[wavrider]

Nothing says great DX better than a low angle of radiation from the antenna at 3/4 of a wave length high/higer for what ever band you have in mind - IMO . . .

Agreed but height also determines what part of the world you will work into.

I have worked Asiatic Russia with the yagi at 55' on 17 meters, 100 watts. right at 1 wl above earth ground.

 

[Robb]

Agreed but height also determines what part of the world you will work into.

I have worked Asiatic Russia with the yagi at 55' on 17 meters, 100 watts. right at 1 wl above earth ground.

I know what you are talkin' about!
Using a cheap Sirio 4 element monoband Yagi on 10m @ 1 wavelength high and 80 watts, I have made nearly 80 different countries/islands just this last fall when long path skip was kicking up well. The low angle of radiation of the beam along with the skip conditions and 1 wavelength high - is the real deal. Moscow, Malaysia, SE Africa, China, and 90% of Europe too.

Since this Fall may be a repeat of last year; now is the right time to get one's DX gear in order - IMO . . .

 

[Captain Kilowatt]

Unless you have stacks of stacks on a rotating tower then you are putting too much thought into take off angles. Get an antenna up as high as you can and do not worry about the TOA. There is no hard brick wall that prevents high angles from working DX to any part of the world. Sometimes things just plain work for whatever reason. Higher is always better regardless of the band. An antenna with a low TOA still has a significant amount of radiation many, many degrees above that angle that will allow shorter distances to be covered into closer target areas. Antennas with a high TOA have some radiation at low angles that will allow long distant DX contacts on occasion. In short, an antenna put up high will pretty much always outperform a lower antenna 98% of the time. If you have the time, real estate, and money to take care of the other 2 % than you are far ahead of most of us.

 

[Robb]

Putting up a antenna @ 1 wave length or greater is easier/cheaper to do for 10m than it is for 20m. That is why I like 10m so much. The antennas are smaller - too . . .

 

[wavrider]

VOACAP Quick Guide: Yagi antennas

Yagi vs height and TAO

 

[wavrider]

CK you have stated exactly what I have found out experimenting with different types of antennas.

It is all M42starduster's fault, he got me back experimenting with wire antennas.

The TOA is important, but no where near the emphasize placed on it.

The lower the take off angle the better the DX performance has always been the rule of thumb.

The simple dipole has DX potential when installed 1/2 wl above ground. The main lobe may be at 30 degrees but there is still radiation at 20 or 15 degrees so it will work for DX.

By installing the Dipole higher research has shown the main lobe starts to break off into other lobes but it is still useful and works well.

The yagi installed at height tends to do the same thing but the lobes are not as broken up or scattered azimuth or elevation wise.

I have 5 acres at the FL QTH to play with for antenna farm and few hundred feet of tower.

In the GA QTH I only have 1.5 acre and couple hundred feet of tower to play with thus I am researching and gathering info as I would like to take the big yagi down from the tower and use nothing but wire antennas installed higher in the air.

Here in Atlanta it seems the weather pounds the location every few years, tornadoes and such, so wires seems to be the way to go.

Robb you are correct the higher freq HF the easier it is to install the yagi at 1 wl.

Unless you have stacks of stacks on a rotating tower then you are putting too much thought into take off angles. Get an antenna up as high as you can and do not worry about the TOA. There is no hard brick wall that prevents high angles from working DX to any part of the world. Sometimes things just plain work for whatever reason. Higher is always better regardless of the band. An antenna with a low TOA still has a significant amount of radiation many, many degrees above that angle that will allow shorter distances to be covered into closer target areas. Antennas with a high TOA have some radiation at low angles that will allow long distant DX contacts on occasion. In short, an antenna put up high will pretty much always outperform a lower antenna 98% of the time. If you have the time, real estate, and money to take care of the other 2 % than you are far ahead of most of us.

 

[Captain Kilowatt]

Putting up a antenna @ 1 wave length or greater is easier/cheaper to do for 10m than it is for 20m. That is why I like 10m so much. The antennas are smaller - too . . .

I have worked all over the world with 100 watts and a beat up ancient A3 tribander installed at a meager 38 feet above ground, basically a half wave length on 20m. 20m has always been and always will be my favourite DX band. Even a beat up old tribander will work worldwide fairly easily even at such a low height. If I listened to everyone that said "You need to be at least a full wavelength high to work DX!" I would have missed an awfull lot of really nice contacts. I have even worked South Africa on 80m with 100 watts into a poorly installed inverted L (too close to a metal tower and no radial field) with only 35 feet vertical and 70 feet horizontal. I can't imagine the TOA of that antenna. My point is that one should install whatever antenna they have/want at whatever height they can manage and not worry about it. It is only in the past 5-6 years I have seen/heard so much talk about antenna height,TOA, azimuthal patterns etc. Most of it seems to be from the newly licensed hams that seem to have studied too hard and practiced too little. The older hams mostly put up an antenna on whatever mast they could muster or nail together and worked the world without regard to what should and shouldn't work. Huge contest stations with mega bucks may benefit from height selection to take advantage of propagation to certain areas but the normal station should just put it up and get on the air.

 

[Mudfoot]

I have also damn near worked the world.

Most contacts were had with a wire never higher than 35'. Granted, a fair amount were made with an 11 meter ground plane. Oh, I did own a V Quad for a few months and I have never owned a base amplifier either.

I will be putting up a hard earned Gainmaster within a week. I'll mainly use it to talk to some old friends about 30 miles away.

I don't sweat the technical stuff. Although, I do understand and comprehend, I just don't bother. I am neither cheap nor poor. I just prefer simple ways. I do admire a big ass tower and antenna and may have one some day, never know.

 

[Robb]

Never said that you - or any body else - needs to do it that way. However, if one wants to optimize what they are doing and already have the resources available to make it happen; then by all means - do so. It is to your own best interest to take advantage of all of the tools available to you or to any one. Learning these things means nothing unless one can realize their value. There is certainly nothing wrong with that idea - IMO.

Once again, 10m is easier to take advantage of this factor - easier than 20m can. Mechanically, electrically, and cost wise.
Not better; certainly - just easier . . .

 

[Marconi]

If you're just looking for number of DX contacts rather than the occasional longest distance contact possible, then maybe a 27' foot pattern in 10-11 meters will do you better and be easier to install than trying to get the height up to 45' feet or higher.

Hopefully you can read this hand written Eznec report on my Imax with 72" horizontal radials, at heights from 9' - 72' feet in 4.5' foot iterations.

This was done to measure 1/4 up to 2 wavelengths in height. Note that each 1/2 wave length indicates something bad is going on, mostly the currents flowing on the mast are the worst for all models, and the random heights in between...are noted to be much better in this regard. I think CK, made a good comment regarding too much attention to the maximum TOA, when DX signals probably arrive in a variety of angles broadside to our vertical antennas. Within reason, lower antennas might be a little better, because the lowest angles are noticeably wider, to receive more signals, than higher antennas with their very narrow lobes at low angles and deep null lobes.

You might also notice that the patterns at 1/2 wave multiples are also noted to show high to very high angle patterns that I note as Bad.

View attachment Imax at various heights..pdf

Remember that these are just models and other considerations must be made, so your mileage may differ.

All models require comparative real world testing in order to be considered a reliable source for what is happening, but modeling could give us some trend indicators for what might happen.

 

[W5LZ]

I think you might also understand that 'C.K.' advised not to obsess about the minimum TOAs, along with 'ideal' heights.
It's all about varying propagation and location. What may be 'ideal' during one stretch of propagation at some particular location may be terrible at a different time. Too many variables for there to be -one- 'ideal' height or TOA.
Get what you can and then quit worrying about it unnecessarily.
- 'Doc

 

[wavrider]

Wonder haw the plots would look for horizontal dipole?

If you're just looking for number of DX contacts rather than the occasional longest distance contact possible, then maybe a 27' foot pattern in 10-11 meters will do you better and be easier to install than trying to get the height up to 45' feet or higher.

Hopefully you can read this hand written Eznec report on my Imax with 72" horizontal radials, at heights from 9' - 72' feet in 4.5' foot iterations.

This was done to measure 1/4 up to 2 wavelengths in height. Note that each 1/2 wave length indicates something bad is going on, mostly the currents flowing on the mast are the worst for all models, and the random heights in between...are noted to be much better in this regard. I think CK, made a good comment regarding too much attention to the maximum TOA, when DX signals probably arrive in a variety of angles broadside to our vertical antennas. Within reason, lower antennas might be a little better, because the lowest angles are noticeably wider, to receive more signals, than higher antennas with their very narrow lobes at low angles and deep null lobes.

You might also notice that the patterns at 1/2 wave multiples are also noted to show high to very high angle patterns that I note as Bad.

View attachment 7404

Remember that these are just models and other considerations must be made, so your mileage may differ.

All models require comparative real world testing in order to be considered a reliable source for what is happening, but modeling could give us some trend indicators for what might happen.

 

[BJ radionut]

Antennas for Receiving and Transmitting

Ask an ye shall receive....
Blows a lot of gain factors out the window...."super antennas" against the lowly dipole....
I found it interesting...
All the Best
BJ


http://www.eham.net/articles/23758 ....another I found interesting....op:
"Factually, take off angle by itself means nothing. Neither does peak gain".....
.....I love that quote!